429 Too Many Requests

Support
#1

The addon map allows to use wms from external source.
But in some cases, the user, by moving or zooming, does too many requests on the WMS endpoint.
OpenLayers get a “429 Too Many Requests” and the tule is not displayed

image

But often the solution is just to call again after a few time.
https://openlayers.org/en/latest/apidoc/module-ol_ImageTile-ImageTile.html

How can I add this code in my app ?
Or maybe could it be added in jmix ?

#3

Hello!

I’ve write a code that sets this function to a WMS source. Could you check that this code resolves the issue? If it works, I would create a GitHub issue to provide the ability to add and configure this function from Maps.

@Subscribe
public void onReady(ReadyEvent event) {
    map.getElement().executeJs("""
            setTimeout(() => {
                const layers = this.olMap.getLayers().getArray();
                for (const layer of layers) {
                    if (layer.constructor.name !== 'TileLayer' || !layer.getSource()) {
                        continue;
                    }
                    const source = layer.getSource();
                    if (source.constructor.name !== 'TileWMS') {
                        continue;
                    }
                    const retryCodes = [408, 429, 500, 502, 503, 504];
                    const retries = {};
                    source.setTileLoadFunction((tile, src) => {
                        const image = tile.getImage();
                        fetch(src)
                          .then((response) => {
                            if (retryCodes.includes(response.status)) {
                              retries[src] = (retries[src] || 0) + 1;
                              if (retries[src] <= 3) {
                                setTimeout(() => tile.load(), retries[src] * 1000);
                              }
                              return Promise.reject();
                            }
                            return response.blob();
                          })
                          .then((blob) => {
                            const imageUrl = URL.createObjectURL(blob);
                            image.src = imageUrl;
                            setTimeout(() => URL.revokeObjectURL(imageUrl), 5000);
                          })
                          .catch(() => tile.setState(3)); // error
                    });
                }
            } , 0);
            """);
}
#5

Thanks! I tested your snippet and it does help, but the issue still persists on our side.
The main cause seems to be that Promise.reject() flows into .catch(() => tile.setState(3)), so the tile is marked as error during the retry phase. Also, three retries is often too few under throttling.
I switched to keeping retries going and honoring Retry-After from the response headers (seconds or HTTP-date); otherwise I use a small capped backoff.
map.element.executeJs("""
setTimeout(() => {
const layers = this.olMap.getLayers().getArray();
for (const layer of layers) {
if (layer.constructor.name !== ‘TileLayer’ || !layer.getSource()) continue;
const source = layer.getSource();
if (source.constructor.name !== ‘TileWMS’) continue;
const retryCodes = [408, 429, 500, 502, 503, 504];
const MAX_BACKOFF_MS = 15000;
const BASE_BACKOFF_MS = 800;
const sleep = (ms) => new Promise(r => setTimeout(r, ms));
source.setTileLoadFunction((tile, src) => {
const image = tile.getImage();
let attempt = 0;
(async function loadForever() {
while (true) {
attempt++;
try {
const resp = await fetch(src);
if (retryCodes.includes(resp.status)) {
const ra = resp.headers.get(‘Retry-After’);
const raMs = ra
? (isNaN(+ra) ? Math.max(0, Date.parse(ra) - Date.now()) : (+ra * 1000))
: Math.min(BASE_BACKOFF_MS * attempt, MAX_BACKOFF_MS);
await sleep(raMs);
continue;
}
const blob = await resp.blob();
const url = URL.createObjectURL(blob);
image.src = url;
setTimeout(() => URL.revokeObjectURL(url), 5000);
break;
} catch (e) {
const delay = Math.min(BASE_BACKOFF_MS * attempt, MAX_BACKOFF_MS);
await sleep(delay);
}
}
})();
});
}
} , 0);
“”");

1 Like
#6

I’ve created a GitHub issue to set this function by default with ability to replace the function by custom one: Provide ability to set tile load function to UrlTile based sources · Issue #4818 · jmix-framework/jmix · GitHub

1 Like